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SubjectRe: [PATCH v2] spi: add OpenCores tiny SPI driver
Hi Grant,

Thanks a lot for the review.

On 01/21/2011 12:54 AM, Grant Likely wrote:
>> drivers/spi/oc_tiny_spi.c | 422 +++++++++++++++++++++++++++++++++++++++
>
> Rename files to spi_oc_tiny.c

OK.

>> +#ifndef CONFIG_TINY_SPI_IDLE_VAL
>> +# define CONFIG_TINY_SPI_IDLE_VAL 0x00
>> +#endif
>
> Do you really want this as a Kconfig symbol? Looks like something
> that should be configured in pdata or the device tree.

I will drop this def, as linux use 00 as default.

>> + if (t->len> 1) {
>> + writeb(CONFIG_TINY_SPI_IDLE_VAL,
>> + hw->base + TINY_SPI_TXDATA);
>> + for (i = 2; i< t->len; i++) {
>> + while (!(readb(hw->base + TINY_SPI_STATUS)&
>> + TINY_SPI_STATUS_TXR))
>> + cpu_relax();
>> + writeb(CONFIG_TINY_SPI_IDLE_VAL,
>> + hw->base + TINY_SPI_TXDATA);
>> + }
>> + }
>> + while (!(readb(hw->base + TINY_SPI_STATUS)&
>> + TINY_SPI_STATUS_TXE))
>> + cpu_relax();
>
> I see a bunch of while loops in this function with no exit condition
> if something goes badly with the hardware. Also, this driver is going
> to chew up *a lot* of cpu cycles when not using irqs. Consider
> putting the polled work into a tasklet instead of blindly spinning.
> It will actually make the driver simpler because the irq and non-irq
> cases become very similar.

But bitbang driver already runs as a workqueue, do we still need to
create a tasklet?

bitbang->workqueue = create_singlethread_workqueue(
dev_name(bitbang->master->dev.parent));

>> + hw->bitbang.master->dev.of_node = pdev->dev.of_node;
>> + val = of_get_property(pdev->dev.of_node, "baud-width", NULL);
>
> 'baud-width'?
>
> These properties need to be documented. See below.

This is the width of baud rate divider. I will document it. Do you have
suggestion on the naming?

>> +#ifdef CONFIG_OF
>> +static struct of_device_id oc_tiny_spi_match[] = {
>> + {
>> + .compatible = "opencores,oc_tiny_spi",
>
> If this is a soft core, then there should be a version number of some
> sort on the compatible value. Also, please use dash '-' instead of
> underscore '_' in compatible values. Also, for all of these new
> bindings, they need to be documented. Please add documentation to
> Documentation/powerpc/dts-bindings (yes, I know, this is not
> for powerpc, but that is the established directory. I'll move it to a
> better location soon).
>
> Finally, one nitpick. For conciseness, most of_device_id tables are
> written in the form:
>
> static struct of_device_id oc_tiny_spi_match[] = {
> { .compatible = "opencores,oc_tiny_spi", }, },
> {},
> }
>

Nice. I am working with Walter on the dts generator for our cores. We
will add them to the listing.

>> +static int __init tiny_spi_init(void)
>> +{
>> + return platform_driver_probe(&tiny_spidrv, tiny_spi_probe);
>> +}
>> +module_init(tiny_spi_init);
>
> Please use platform_driver_register, and put your probe function into
> the platform_driver structure.
>

OK. I will do the same for spi_altera.

Best regards,
Thomas


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